/**
 *
 */
package com.synjones.tsm.test.crypto;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
/**
 * @author jun.lijun
 *
 */
public class Base64 {
  private static final char[] S_BASE64CHAR = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
  private static final char S_BASE64PAD = '=';
  private static final byte[] S_DECODETABLE = new byte[128];
  static {
    for (int i = 0; i < S_DECODETABLE.length; i++)
      S_DECODETABLE[i] = Byte.MAX_VALUE;  // 127
    for (int i = 0; i < S_BASE64CHAR.length; i++) // 0 to 63
      S_DECODETABLE[S_BASE64CHAR[i]] = (byte) i;
  }
  private static int decode0(char[] ibuf, byte[] obuf, int wp) {
    int outlen = 3;
    if (ibuf[3] == S_BASE64PAD)
      outlen = 2;
    if (ibuf[2] == S_BASE64PAD)
      outlen = 1;
    int b0 = S_DECODETABLE[ibuf[0]];
    int b1 = S_DECODETABLE[ibuf[1]];
    int b2 = S_DECODETABLE[ibuf[2]];
    int b3 = S_DECODETABLE[ibuf[3]];
    switch (outlen) {
      case 1:
        obuf[wp] = (byte) (b0 << 2 & 0xfc | b1 >> 4 & 0x3);
        return 1;
      case 2:
        obuf[wp++] = (byte) (b0 << 2 & 0xfc | b1 >> 4 & 0x3);
        obuf[wp] = (byte) (b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
        return 2;
      case 3:
        obuf[wp++] = (byte) (b0 << 2 & 0xfc | b1 >> 4 & 0x3);
        obuf[wp++] = (byte) (b1 << 4 & 0xf0 | b2 >> 2 & 0xf);
        obuf[wp] = (byte) (b2 << 6 & 0xc0 | b3 & 0x3f);
        return 3;
      default:
        throw new RuntimeException("Couldn't decode.");
    }
  }
  /**
   *
   */
  public static byte[] decode(char[] data, int off, int len) {
    char[] ibuf = new char[4];
    int ibufcount = 0;
    byte[] obuf = new byte[len / 4 * 3 + 3];
    int obufcount = 0;
    for (int i = off; i < off + len; i++) {
      char ch = data[i];
      if (ch == S_BASE64PAD || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
        ibuf[ibufcount++] = ch;
        if (ibufcount == ibuf.length) {
          ibufcount = 0;
          obufcount += decode0(ibuf, obuf, obufcount);
        }
      }
    }
    if (obufcount == obuf.length)
      return obuf;
    byte[] ret = new byte[obufcount];
    System.arraycopy(obuf, 0, ret, 0, obufcount);
    return ret;
  }
  /**
   *
   */
  public static byte[] decode(String data) {
    char[] ibuf = new char[4];
    int ibufcount = 0;
    byte[] obuf = new byte[data.length() / 4 * 3 + 3];
    int obufcount = 0;
    for (int i = 0; i < data.length(); i++) {
      char ch = data.charAt(i);
      if (ch == S_BASE64PAD || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
        ibuf[ibufcount++] = ch;
        if (ibufcount == ibuf.length) {
          ibufcount = 0;
          obufcount += decode0(ibuf, obuf, obufcount);
        }
      }
    }
    if (obufcount == obuf.length)
      return obuf;
    byte[] ret = new byte[obufcount];
    System.arraycopy(obuf, 0, ret, 0, obufcount);
    return ret;
  }
  /**
   *
   */
  public static void decode(char[] data, int off, int len, OutputStream ostream) throws IOException {
    char[] ibuf = new char[4];
    int ibufcount = 0;
    byte[] obuf = new byte[3];
    for (int i = off; i < off + len; i++) {
      char ch = data[i];
      if (ch == S_BASE64PAD || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
        ibuf[ibufcount++] = ch;
        if (ibufcount == ibuf.length) {
          ibufcount = 0;
          int obufcount = decode0(ibuf, obuf, 0);
          ostream.write(obuf, 0, obufcount);
        }
      }
    }
  }
  /**
   *
   */
  public static void decode(String data, OutputStream ostream) throws IOException {
    char[] ibuf = new char[4];
    int ibufcount = 0;
    byte[] obuf = new byte[3];
    for (int i = 0; i < data.length(); i++) {
      char ch = data.charAt(i);
      if (ch == S_BASE64PAD || ch < S_DECODETABLE.length && S_DECODETABLE[ch] != Byte.MAX_VALUE) {
        ibuf[ibufcount++] = ch;
        if (ibufcount == ibuf.length) {
          ibufcount = 0;
          int obufcount = decode0(ibuf, obuf, 0);
          ostream.write(obuf, 0, obufcount);
        }
      }
    }
  }
  /**
   * Returns base64 representation of specified byte array.
   */
  public static String encode(byte[] data) {
    return encode(data, 0, data.length);
  }
  /**
   * Returns base64 representation of specified byte array.
   */
  public static String encode(byte[] data, int off, int len) {
    if (len <= 0)
      return "";
    char[] out = new char[len / 3 * 4 + 4];
    int rindex = off;
    int windex = 0;
    int rest = len - off;
    while (rest >= 3) {
      int i = ((data[rindex] & 0xff) << 16) + ((data[rindex + 1] & 0xff) << 8) + (data[rindex + 2] & 0xff);
      out[windex++] = S_BASE64CHAR[i >> 18];
      out[windex++] = S_BASE64CHAR[(i >> 12) & 0x3f];
      out[windex++] = S_BASE64CHAR[(i >> 6) & 0x3f];
      out[windex++] = S_BASE64CHAR[i & 0x3f];
      rindex += 3;
      rest -= 3;
    }
    if (rest == 1) {
      int i = data[rindex] & 0xff;
      out[windex++] = S_BASE64CHAR[i >> 2];
      out[windex++] = S_BASE64CHAR[(i << 4) & 0x3f];
      out[windex++] = S_BASE64PAD;
      out[windex++] = S_BASE64PAD;
    }
    else if (rest == 2) {
      int i = ((data[rindex] & 0xff) << 8) + (data[rindex + 1] & 0xff);
      out[windex++] = S_BASE64CHAR[i >> 10];
      out[windex++] = S_BASE64CHAR[(i >> 4) & 0x3f];
      out[windex++] = S_BASE64CHAR[(i << 2) & 0x3f];
      out[windex++] = S_BASE64PAD;
    }
    return new String(out, 0, windex);
  }
  /**
   * Outputs base64 representation of the specified byte array to a byte stream.
   */
  public static void encode(byte[] data, int off, int len, OutputStream ostream) throws IOException {
    if (len <= 0)
      return;
    byte[] out = new byte[4];
    int rindex = off;
    int rest = len - off;
    while (rest >= 3) {
      int i = ((data[rindex] & 0xff) << 16) + ((data[rindex + 1] & 0xff) << 8) + (data[rindex + 2] & 0xff);
      out[0] = (byte) S_BASE64CHAR[i >> 18];
      out[1] = (byte) S_BASE64CHAR[(i >> 12) & 0x3f];
      out[2] = (byte) S_BASE64CHAR[(i >> 6) & 0x3f];
      out[3] = (byte) S_BASE64CHAR[i & 0x3f];
      ostream.write(out, 0, 4);
      rindex += 3;
      rest -= 3;
    }
    if (rest == 1) {
      int i = data[rindex] & 0xff;
      out[0] = (byte) S_BASE64CHAR[i >> 2];
      out[1] = (byte) S_BASE64CHAR[(i << 4) & 0x3f];
      out[2] = (byte) S_BASE64PAD;
      out[3] = (byte) S_BASE64PAD;
      ostream.write(out, 0, 4);
    }
    else if (rest == 2) {
      int i = ((data[rindex] & 0xff) << 8) + (data[rindex + 1] & 0xff);
      out[0] = (byte) S_BASE64CHAR[i >> 10];
      out[1] = (byte) S_BASE64CHAR[(i >> 4) & 0x3f];
      out[2] = (byte) S_BASE64CHAR[(i << 2) & 0x3f];
      out[3] = (byte) S_BASE64PAD;
      ostream.write(out, 0, 4);
    }
  }
  /**
   * Outputs base64 representation of the specified byte array to a character stream.
   */
  public static void encode(byte[] data, int off, int len, Writer writer) throws IOException {
    if (len <= 0)
      return;
    char[] out = new char[4];
    int rindex = off;
    int rest = len - off;
    int output = 0;
    while (rest >= 3) {
      int i = ((data[rindex] & 0xff) << 16) + ((data[rindex + 1] & 0xff) << 8) + (data[rindex + 2] & 0xff);
      out[0] = S_BASE64CHAR[i >> 18];
      out[1] = S_BASE64CHAR[(i >> 12) & 0x3f];
      out[2] = S_BASE64CHAR[(i >> 6) & 0x3f];
      out[3] = S_BASE64CHAR[i & 0x3f];
      writer.write(out, 0, 4);
      rindex += 3;
      rest -= 3;
      output += 4;
      if (output % 76 == 0)
        writer.write("\n");
    }
    if (rest == 1) {
      int i = data[rindex] & 0xff;
      out[0] = S_BASE64CHAR[i >> 2];
      out[1] = S_BASE64CHAR[(i << 4) & 0x3f];
      out[2] = S_BASE64PAD;
      out[3] = S_BASE64PAD;
      writer.write(out, 0, 4);
    }
    else if (rest == 2) {
      int i = ((data[rindex] & 0xff) << 8) + (data[rindex + 1] & 0xff);
      out[0] = S_BASE64CHAR[i >> 10];
      out[1] = S_BASE64CHAR[(i >> 4) & 0x3f];
      out[2] = S_BASE64CHAR[(i << 2) & 0x3f];
      out[3] = S_BASE64PAD;
      writer.write(out, 0, 4);
    }
  }
}
